#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
	char a[20],s[20];
	int i,top,mid,len,next;
	gets(a);
	len=strlen(a);
	mid=len/2-1;
	top=0;
	for(i=0;i<=mid;i++){
		top++;
		s[top]=a[i];
	}
	if(i%2==0)next=mid+1;
	else next=mid+2;
	for(i=next;i<len;i++){
		if(a[i]!=s[top])break;
		top--;
		
	}
	if(top==0)printf("yes");
	else printf("no");

    return 0;
}
